Factual error: Boxes of Krispy Kreme doughnuts are seen in several episodes; there were no Krispy Kreme locations in Wisconsin until after 2000.
Factual error: In the intro theme, most of the cars in the background are newer then the set time period. About halfway, you see an at least 1997 Ford F-150 pickup drive by the left windows, not manufactured yet.
Continuity mistake: In the second episode of the series Eric's Birthday is in May. The second episode of season 5 Eric says his birthday is in March. In season 6 Eric's Birthday occurs after graduation, which would make his birthday after June.
Factual error: Several times, Fez claims to love the book "Superfudge", reading it once a month. However, it wasn't published until 1980.
Other mistake: How did Donna take the SATs with the rest of the group if she was going to a different school? She is even wearing her catholic school uniform.
Factual error: At the start of every episode we see the gang driving. Cars in the background are not from the 70s but the late 90s. For instance, the truck that comes up beside them at the end is a 90s Ford F150.
Factual error: Eric has diecast model cars in his bedroom; those were not around then. The ones he has weren't available until the 1990s.
Chosen answer: He isn't. Time moves slowly in the show because they didn't want it to turn into "That '80's Show". In the first episode, he say's he's 17 but the second episode was his 17th birthday so he must have been 16. The first 12 episodes are set in 1976, the next 2 seasons are set in 1977, the next 3 seasons are set in 1978, and the remaining shows take place in 1979 with the final show on Dec 31, 1979 when Eric must be 20 as he turned 17 in 1976.
Myridon